This blog contains Multiple Choice questions in Microbiology and related disciplines (Virology, Parasitology,
Mycology, Bacteriology, Genetics)
and Notes for all the related disciplines.

Tuesday, April 20, 2010

Salk and sabin vaccine (T.U 2063)

Salk and sabin vaccine (T.U 2063)

Two types of vaccine are available against poliomyelitis, inactivated vaccine (IPV, Salk) and live attenuated oral vaccine (OPV, Sabin). Both vaccine formulations contain all three polio types.

Sabin or OPV

OPV is the most widely used vaccine for prevention of poliomyelitis. It is composed of attenuated strains of the three poliovirus types, and is administered orally.

At least two or three doses are considered necessary to ensure adequate immunity, in some countries even five to six or more doses are given in the primary course. Revaccination is used to a varying degree. A full primary course induces an antibody response against all three types in more than 90% of vaccinees and gives a high degree of protection against disease. OPV also induces intestinal immunity due to production of secretory IgA antibodies. This is important for inhibition of virus replication in the gut, diminishing the possible spread of virus to susceptible contacts. OPV is almost

non-reactogenic, and is very safe. However, in a few cases an attenuated vaccine strain may induce paralytic disease. This occurs in about one case per 1–10 million vaccine doses administered.

Salk or IPV

IPV was the first vaccine used against poliomyelitis. It contains the three types of poliovirus inactivated by formaldehyde and is administered parenterally. The use of IPV in the late 1950s was followed by a 90% reduction of poliomyelitis cases when it was replaced in many countries by the more easily administered OPV around 1960. Newer IPVs have higher immunogenic potency which has led to a reintroduction of IPV in many developed and developing countries. The primary vaccination course with IPV consists of two or three doses, usually followed by revaccination after intervals of about 5–10 years during childhood and adolescence. Some countries are using a combination of OPV and IPV.